(a) Field of the Invention
The present invention relates to a signal transmitting apparatus and a method thereof. More particularly, the present invention relates to a signal transmitting apparatus that efficiently reduces a time delay and a memory use amount when a cyclic prefix is added at a transmission end of an OFDM (orthogonal frequency division multiplexing) system, to a method thereof, and to an inverse fast Fourier transform (IFFT) apparatus for a signal transmitting apparatus.
(b) Description of the Related Art
At a transmitting end of an OFDM system, an inverse FFT (inverse fast Fourier transform; hereinafter referred to as “IFFT”) computation is performed, and then a last portion of each OFDM symbol is added to a front portion of the symbol as a cyclic prefix (hereinafter referred to as “CP”) to complete a single OFDM symbol.
Here, the cyclic prefix is inserted to prevent orthogonality from being destroyed due to a subcarrier delay.
The transmitting end in the known OFDM system will be described with reference to FIG. 1.
FIG. 1 is a block diagram showing a transmitting end of a known OFDM system.
As shown in FIG. 1, a transmitting end of a known OFDM system includes a QAM (quadrature amplitude modulation) mapper 100, a carrier randomizer 110, a memory 120, an IFFT unit 130, and a symbol re-ordering memory 140.
The QAM mapper 100 and the carrier randomizer 110 perform symbol allocation and carrier insertion on received source data.
The memory 120 temporarily stores data that is transmitted from the carrier randomizer 110 and sequentially transmits the data to the IFFT unit 130. Then, the IFFT unit 130 performs the inverse fast Fourier transform (IFFT) on the received data and transmits the transformed data to the symbol re-ordering memory 140.
The symbol re-ordering memory 140 adds the last portion of the symbol transmitted from the IFFT unit 130 to the head of the symbol to generate a single OFDM symbol, and transmits the generated OFDM symbol.
At the transmitting end of the known OFDM system, as shown in FIG. 2, since the last one of the result values of the inverse fast Fourier transform (IFFT) is added to the head of the symbol, it is necessary to store all of the result values of the inverse fast Fourier transform (IFFT) in the memory and then read all of the result values. Accordingly, as shown in FIG. 2, there is a problem in that a time delay occurs. In addition, since it is necessary to read all of the result values of the inverse fast Fourier transform (IFFT), an additional memory is needed within the transmitting end of the OFDM system.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.